Calculating percentage change

Hello, I need to find the percentage change from one number to another. For example, the costs in 2008 were $40, 000 and the costs in 2009 were $35,000. How would I go about finding the change in percentage between those two costs? Is there a general formula?

There is a formula

Percentage change implies some quantity at two points in time. Percentage change is the AMOUNT of change from one point in time to the next divided by the ORIGINAL amount, chronologically, times 100 to convert the decimal to a percent. Try doing that.